""" Multicast DNS Service Discovery for Python, v0.12
    Copyright (C) 2003, Paul Scott-Murphy

    This module provides a framework for the use of DNS Service Discovery
    using IP multicast.  It has been tested against the JRendezvous
    implementation from <a href="http://strangeberry.com">StrangeBerry</a>,
    and against the mDNSResponder from Mac OS X 10.3.8.

    This library is free software; you can redistribute it and/or
    modify it under the terms of the GNU Lesser General Public
    License as published by the Free Software Foundation; either
    version 2.1 of the License, or (at your option) any later version.

    This library is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
    Lesser General Public License for more details.

    You should have received a copy of the GNU Lesser General Public
    License along with this library; if not, write to the Free Software
    Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
  
"""

"""0.12 update - allow selection of binding interface
     typo fix - Thanks A. M. Kuchlingi
     removed all use of word 'Rendezvous' - this is an API change"""

"""0.11 update - correction to comments for addListener method
                 support for new record types seen from OS X
          - IPv6 address
          - hostinfo
         ignore unknown DNS record types
         fixes to name decoding
         works alongside other processes using port 5353 (e.g. on Mac OS X)
         tested against Mac OS X 10.3.2's mDNSResponder
         corrections to removal of list entries for service browser"""

"""0.10 update - Jonathon Paisley contributed these corrections:
                 always multicast replies, even when query is unicast
         correct a pointer encoding problem
         can now write records in any order
         traceback shown on failure
         better TXT record parsing
         server is now separate from name
         can cancel a service browser

         modified some unit tests to accommodate these changes"""

"""0.09 update - remove all records on service unregistration
                 fix DOS security problem with readName"""

"""0.08 update - changed licensing to LGPL"""

"""0.07 update - faster shutdown on engine
                 pointer encoding of outgoing names
         ServiceBrowser now works
         new unit tests"""

"""0.06 update - small improvements with unit tests
                 added defined exception types
         new style objects
         fixed hostname/interface problem
         fixed socket timeout problem
         fixed addServiceListener() typo bug
         using select() for socket reads
         tested on Debian unstable with Python 2.2.2"""

"""0.05 update - ensure case insensitivty on domain names
                 support for unicast DNS queries"""

"""0.04 update - added some unit tests
                 added __ne__ adjuncts where required
         ensure names end in '.local.'
         timeout on receiving socket for clean shutdown"""

__author__ = "Paul Scott-Murphy"
__email__ = "paul at scott dash murphy dot com"
__version__ = "0.12"

import string
import time
import struct
import socket
import threading
import select
import traceback

__all__ = ["Zeroconf", "ServiceInfo", "ServiceBrowser"]

# hook for threads

globals()['_GLOBAL_DONE'] = 0

# Some timing constants

_UNREGISTER_TIME = 125
_CHECK_TIME = 175
_REGISTER_TIME = 225
_LISTENER_TIME = 200
_BROWSER_TIME = 500

# Some DNS constants
  
_MDNS_ADDR = '224.0.0.251'
_MDNS_PORT = 5353;
_DNS_PORT = 53;
_DNS_TTL = 60 * 60; # one hour default TTL

_MAX_MSG_TYPICAL = 1460 # unused
_MAX_MSG_ABSOLUTE = 8972

_FLAGS_QR_MASK = 0x8000 # query response mask
_FLAGS_QR_QUERY = 0x0000 # query
_FLAGS_QR_RESPONSE = 0x8000 # response

_FLAGS_AA = 0x0400 # Authorative answer
_FLAGS_TC = 0x0200 # Truncated
_FLAGS_RD = 0x0100 # Recursion desired
_FLAGS_RA = 0x8000 # Recursion available

_FLAGS_Z = 0x0040 # Zero
_FLAGS_AD = 0x0020 # Authentic data
_FLAGS_CD = 0x0010 # Checking disabled

_CLASS_IN = 1
_CLASS_CS = 2
_CLASS_CH = 3
_CLASS_HS = 4
_CLASS_NONE = 254
_CLASS_ANY = 255
_CLASS_MASK = 0x7FFF
_CLASS_UNIQUE = 0x8000

_TYPE_A = 1
_TYPE_NS = 2
_TYPE_MD = 3
_TYPE_MF = 4
_TYPE_CNAME = 5
_TYPE_SOA = 6
_TYPE_MB = 7
_TYPE_MG = 8
_TYPE_MR = 9
_TYPE_NULL = 10
_TYPE_WKS = 11
_TYPE_PTR = 12
_TYPE_HINFO = 13
_TYPE_MINFO = 14
_TYPE_MX = 15
_TYPE_TXT = 16
_TYPE_AAAA = 28
_TYPE_SRV = 33
_TYPE_ANY =  255

# Mapping constants to names

_CLASSES = { _CLASS_IN : "in",
       _CLASS_CS : "cs",
       _CLASS_CH : "ch",
       _CLASS_HS : "hs",
       _CLASS_NONE : "none",
       _CLASS_ANY : "any" }

_TYPES = { _TYPE_A : "a",
       _TYPE_NS : "ns",
       _TYPE_MD : "md",
       _TYPE_MF : "mf",
       _TYPE_CNAME : "cname",
       _TYPE_SOA : "soa",
       _TYPE_MB : "mb",
       _TYPE_MG : "mg",
       _TYPE_MR : "mr",
       _TYPE_NULL : "null",
       _TYPE_WKS : "wks",
       _TYPE_PTR : "ptr",
       _TYPE_HINFO : "hinfo",
       _TYPE_MINFO : "minfo",
       _TYPE_MX : "mx",
       _TYPE_TXT : "txt",
       _TYPE_AAAA : "quada",
       _TYPE_SRV : "srv",
       _TYPE_ANY : "any" }

# utility functions

def currentTimeMillis():
  """Current system time in milliseconds"""
  return time.time() * 1000

# Exceptions

class NonLocalNameException(Exception):
  pass

class NonUniqueNameException(Exception):
  pass

class NamePartTooLongException(Exception):
  pass

class AbstractMethodException(Exception):
  pass

class BadTypeInNameException(Exception):
  pass

# implementation classes

class DNSEntry(object):
  """A DNS entry"""
  
  def __init__(self, name, type, clazz):
    self.key = string.lower(name)
    self.name = name
    self.type = type
    self.clazz = clazz & _CLASS_MASK
    self.unique = (clazz & _CLASS_UNIQUE) != 0

  def __eq__(self, other):
    """Equality test on name, type, and class"""
    if isinstance(other, DNSEntry):
      return self.name == other.name and self.type == other.type and self.clazz == other.clazz
    return 0

  def __ne__(self, other):
    """Non-equality test"""
    return not self.__eq__(other)

  def getClazz(self, clazz):
    """Class accessor"""
    try:
      return _CLASSES[clazz]
    except:
      return "?(%s)" % (clazz)

  def getType(self, type):
    """Type accessor"""
    try:
      return _TYPES[type]
    except:
      return "?(%s)" % (type)

  def toString(self, hdr, other):
    """String representation with additional information"""
    result = "%s[%s,%s" % (hdr, self.getType(self.type), self.getClazz(self.clazz))
    if self.unique:
      result += "-unique,"
    else:
      result += ","
    result += self.name
    if other is not None:
      result += ",%s]" % (other)
    else:
      result += "]"
    return result

class DNSQuestion(DNSEntry):
  """A DNS question entry"""
  
  def __init__(self, name, type, clazz):
    if not name.endswith(".local."):
      raise NonLocalNameException
    DNSEntry.__init__(self, name, type, clazz)

  def answeredBy(self, rec):
    """Returns true if the question is answered by the record"""
    return self.clazz == rec.clazz and (self.type == rec.type or self.type == _TYPE_ANY) and self.name == rec.name

  def __repr__(self):
    """String representation"""
    return DNSEntry.toString(self, "question", None)


class DNSRecord(DNSEntry):
  """A DNS record - like a DNS entry, but has a TTL"""
  
  def __init__(self, name, type, clazz, ttl):
    DNSEntry.__init__(self, name, type, clazz)
    self.ttl = ttl
    self.created = currentTimeMillis()

  def __eq__(self, other):
    """Tests equality as per DNSRecord"""
    if isinstance(other, DNSRecord):
      return DNSEntry.__eq__(self, other)
    return 0

  def suppressedBy(self, msg):
    """Returns true if any answer in a message can suffice for the
    information held in this record."""
    for record in msg.answers:
      if self.suppressedByAnswer(record):
        return 1
    return 0

  def suppressedByAnswer(self, other):
    """Returns true if another record has same name, type and class,
    and if its TTL is at least half of this record's."""
    if self == other and other.ttl > (self.ttl / 2):
      return 1
    return 0

  def getExpirationTime(self, percent):
    """Returns the time at which this record will have expired
    by a certain percentage."""
    return self.created + (percent * self.ttl * 10)

  def getRemainingTTL(self, now):
    """Returns the remaining TTL in seconds."""
    return max(0, (self.getExpirationTime(100) - now) / 1000)

  def isExpired(self, now):
    """Returns true if this record has expired."""
    return self.getExpirationTime(100) <= now

  def isStale(self, now):
    """Returns true if this record is at least half way expired."""
    return self.getExpirationTime(50) <= now

  def resetTTL(self, other):
    """Sets this record's TTL and created time to that of
    another record."""
    self.created = other.created
    self.ttl = other.ttl

  def write(self, out):
    """Abstract method"""
    raise AbstractMethodException

  def toString(self, other):
    """String representation with addtional information"""
    arg = "%s/%s,%s" % (self.ttl, self.getRemainingTTL(currentTimeMillis()), other)
    return DNSEntry.toString(self, "record", arg)

class DNSAddress(DNSRecord):
  """A DNS address record"""
  
  def __init__(self, name, type, clazz, ttl, address):
    DNSRecord.__init__(self, name, type, clazz, ttl)
    self.address = address

  def write(self, out):
    """Used in constructing an outgoing packet"""
    out.writeString(self.address, len(self.address))

  def __eq__(self, other):
    """Tests equality on address"""
    if isinstance(other, DNSAddress):
      return self.address == other.address
    return 0

  def __repr__(self):
    """String representation"""
    try:
      return socket.inet_ntoa(self.address)
    except:
      return self.address

class DNSHinfo(DNSRecord):
  """A DNS host information record"""

  def __init__(self, name, type, clazz, ttl, cpu, os):
    DNSRecord.__init__(self, name, type, clazz, ttl)
    self.cpu = cpu
    self.os = os

  def write(self, out):
    """Used in constructing an outgoing packet"""
    out.writeString(self.cpu, len(self.cpu))
    out.writeString(self.os, len(self.os))

  def __eq__(self, other):
    """Tests equality on cpu and os"""
    if isinstance(other, DNSHinfo):
      return self.cpu == other.cpu and self.os == other.os
    return 0

  def __repr__(self):
    """String representation"""
    return self.cpu + " " + self.os
  
class DNSPointer(DNSRecord):
  """A DNS pointer record"""
  
  def __init__(self, name, type, clazz, ttl, alias):
    DNSRecord.__init__(self, name, type, clazz, ttl)
    self.alias = alias

  def write(self, out):
    """Used in constructing an outgoing packet"""
    out.writeName(self.alias)

  def __eq__(self, other):
    """Tests equality on alias"""
    if isinstance(other, DNSPointer):
      return self.alias == other.alias
    return 0

  def __repr__(self):
    """String representation"""
    return self.toString(self.alias)

class DNSText(DNSRecord):
  """A DNS text record"""
  
  def __init__(self, name, type, clazz, ttl, text):
    DNSRecord.__init__(self, name, type, clazz, ttl)
    self.text = text

  def write(self, out):
    """Used in constructing an outgoing packet"""
    out.writeString(self.text, len(self.text))

  def __eq__(self, other):
    """Tests equality on text"""
    if isinstance(other, DNSText):
      return self.text == other.text
    return 0

  def __repr__(self):
    """String representation"""
    if len(self.text) > 10:
      return self.toString(self.text[:7] + "...")
    else:
      return self.toString(self.text)

class DNSService(DNSRecord):
  """A DNS service record"""
  
  def __init__(self, name, type, clazz, ttl, priority, weight, port, server):
    DNSRecord.__init__(self, name, type, clazz, ttl)
    self.priority = priority
    self.weight = weight
    self.port = port
    self.server = server

  def write(self, out):
    """Used in constructing an outgoing packet"""
    out.writeShort(self.priority)
    out.writeShort(self.weight)
    out.writeShort(self.port)
    out.writeName(self.server)

  def __eq__(self, other):
    """Tests equality on priority, weight, port and server"""
    if isinstance(other, DNSService):
      return self.priority == other.priority and self.weight == other.weight and self.port == other.port and self.server == other.server
    return 0

  def __repr__(self):
    """String representation"""
    return self.toString("%s:%s" % (self.server, self.port))

class DNSIncoming(object):
  """Object representation of an incoming DNS packet"""
  
  def __init__(self, data):
    """Constructor from string holding bytes of packet"""
    self.offset = 0
    self.data = data
    self.questions = []
    self.answers = []
    self.numQuestions = 0
    self.numAnswers = 0
    self.numAuthorities = 0
    self.numAdditionals = 0
    
    self.readHeader()
    self.readQuestions()
    self.readOthers()

  def readHeader(self):
    """Reads header portion of packet"""
    format = '!HHHHHH'
    length = struct.calcsize(format)
    info = struct.unpack(format, self.data[self.offset:self.offset+length])
    self.offset += length

    self.id = info[0]
    self.flags = info[1]
    self.numQuestions = info[2]
    self.numAnswers = info[3]
    self.numAuthorities = info[4]
    self.numAdditionals = info[5]

  def readQuestions(self):
    """Reads questions section of packet"""
    format = '!HH'
    length = struct.calcsize(format)
    for i in range(0, self.numQuestions):
      name = self.readName()
      info = struct.unpack(format, self.data[self.offset:self.offset+length])
      self.offset += length
      
      question = DNSQuestion(name, info[0], info[1])
      self.questions.append(question)

  def readInt(self):
    """Reads an integer from the packet"""
    format = '!I'
    length = struct.calcsize(format)
    info = struct.unpack(format, self.data[self.offset:self.offset+length])
    self.offset += length
    return info[0]

  def readCharacterString(self):
    """Reads a character string from the packet"""
    length = ord(self.data[self.offset])
    self.offset += 1
    return self.readString(length)

  def readString(self, len):
    """Reads a string of a given length from the packet"""
    format = '!' + str(len) + 's'
    length =  struct.calcsize(format)
    info = struct.unpack(format, self.data[self.offset:self.offset+length])
    self.offset += length
    return info[0]

  def readUnsignedShort(self):
    """Reads an unsigned short from the packet"""
    format = '!H'
    length = struct.calcsize(format)
    info = struct.unpack(format, self.data[self.offset:self.offset+length])
    self.offset += length
    return info[0]

  def readOthers(self):
    """Reads the answers, authorities and additionals section of the packet"""
    format = '!HHiH'
    length = struct.calcsize(format)
    n = self.numAnswers + self.numAuthorities + self.numAdditionals
    for i in range(0, n):
      domain = self.readName()
      info = struct.unpack(format, self.data[self.offset:self.offset+length])
      self.offset += length

      rec = None
      if info[0] == _TYPE_A:
        rec = DNSAddress(domain, info[0], info[1], info[2], self.readString(4))
      elif info[0] == _TYPE_CNAME or info[0] == _TYPE_PTR:
        rec = DNSPointer(domain, info[0], info[1], info[2], self.readName())
      elif info[0] == _TYPE_TXT:
        rec = DNSText(domain, info[0], info[1], info[2], self.readString(info[3]))
      elif info[0] == _TYPE_SRV:
        rec = DNSService(domain, info[0], info[1], info[2], self.readUnsignedShort(), self.readUnsignedShort(), self.readUnsignedShort(), self.readName())
      elif info[0] == _TYPE_HINFO:
        rec = DNSHinfo(domain, info[0], info[1], info[2], self.readCharacterString(), self.readCharacterString())
      elif info[0] == _TYPE_AAAA:
        rec = DNSAddress(domain, info[0], info[1], info[2], self.readString(16))
      else:
        # Try to ignore types we don't know about
        # this may mean the rest of the name is
        # unable to be parsed, and may show errors
        # so this is left for debugging.  New types
        # encountered need to be parsed properly.
        #
        #print "UNKNOWN TYPE = " + str(info[0])
        #raise BadTypeInNameException
        pass

      if rec is not None:
        self.answers.append(rec)
        
  def isQuery(self):
    """Returns true if this is a query"""
    return (self.flags & _FLAGS_QR_MASK) == _FLAGS_QR_QUERY

  def isResponse(self):
    """Returns true if this is a response"""
    return (self.flags & _FLAGS_QR_MASK) == _FLAGS_QR_RESPONSE

  def readUTF(self, offset, len):
    """Reads a UTF-8 string of a given length from the packet"""
    result = self.data[offset:offset+len].decode('utf-8')
    return result
    
  def readName(self):
    """Reads a domain name from the packet"""
    result = ''
    off = self.offset
    next = -1
    first = off

    while 1:
      len = ord(self.data[off])
      off += 1
      if len == 0:
        break
      t = len & 0xC0
      if t == 0x00:
        result = ''.join((result, self.readUTF(off, len) + '.'))
        off += len
      elif t == 0xC0:
        if next < 0:
          next = off + 1
        off = ((len & 0x3F) << 8) | ord(self.data[off])
        if off >= first:
          raise "Bad domain name (circular) at " + str(off)
        first = off
      else:
        raise "Bad domain name at " + str(off)

    if next >= 0:
      self.offset = next
    else:
      self.offset = off

    return result
  
    
class DNSOutgoing(object):
  """Object representation of an outgoing packet"""
  
  def __init__(self, flags, multicast = 1):
    self.finished = 0
    self.id = 0
    self.multicast = multicast
    self.flags = flags
    self.names = {}
    self.data = []
    self.size = 12
    
    self.questions = []
    self.answers = []
    self.authorities = []
    self.additionals = []

  def addQuestion(self, record):
    """Adds a question"""
    self.questions.append(record)

  def addAnswer(self, inp, record):
    """Adds an answer"""
    if not record.suppressedBy(inp):
      self.addAnswerAtTime(record, 0)

  def addAnswerAtTime(self, record, now):
    """Adds an answer if if does not expire by a certain time"""
    if record is not None:
      if now == 0 or not record.isExpired(now):
        self.answers.append((record, now))

  def addAuthorativeAnswer(self, record):
    """Adds an authoritative answer"""
    self.authorities.append(record)

  def addAdditionalAnswer(self, record):
    """Adds an additional answer"""
    self.additionals.append(record)

  def writeByte(self, value):
    """Writes a single byte to the packet"""
    format = '!c'
    self.data.append(struct.pack(format, chr(value)))
    self.size += 1

  def insertShort(self, index, value):
    """Inserts an unsigned short in a certain position in the packet"""
    format = '!H'
    self.data.insert(index, struct.pack(format, value))
    self.size += 2
    
  def writeShort(self, value):
    """Writes an unsigned short to the packet"""
    format = '!H'
    self.data.append(struct.pack(format, value))
    self.size += 2

  def writeInt(self, value):
    """Writes an unsigned integer to the packet"""
    format = '!I'
    self.data.append(struct.pack(format, int(value)))
    self.size += 4

  def writeString(self, value, length):
    """Writes a string to the packet"""
    format = '!' + str(length) + 's'
    self.data.append(struct.pack(format, value))
    self.size += length

  def writeUTF(self, s):
    """Writes a UTF-8 string of a given length to the packet"""
    utfstr = s.encode('utf-8')
    length = len(utfstr)
    if length > 64:
      raise NamePartTooLongException
    self.writeByte(length)
    self.writeString(utfstr, length)

  def writeName(self, name):
    """Writes a domain name to the packet"""

    try:
      # Find existing instance of this name in packet
      #
      index = self.names[name]
    except KeyError:
      # No record of this name already, so write it
      # out as normal, recording the location of the name
      # for future pointers to it.
      #
      self.names[name] = self.size
      parts = name.split('.')
      if parts[-1] == '':
        parts = parts[:-1]
      for part in parts:
        self.writeUTF(part)
      self.writeByte(0)
      return

    # An index was found, so write a pointer to it
    #
    self.writeByte((index >> 8) | 0xC0)
    self.writeByte(index)

  def writeQuestion(self, question):
    """Writes a question to the packet"""
    self.writeName(question.name)
    self.writeShort(question.type)
    self.writeShort(question.clazz)

  def writeRecord(self, record, now):
    """Writes a record (answer, authoritative answer, additional) to
    the packet"""
    self.writeName(record.name)
    self.writeShort(record.type)
    if record.unique and self.multicast:
      self.writeShort(record.clazz | _CLASS_UNIQUE)
    else:
      self.writeShort(record.clazz)
    if now == 0:
      self.writeInt(record.ttl)
    else:
      self.writeInt(record.getRemainingTTL(now))
    index = len(self.data)
    # Adjust size for the short we will write before this record
    #
    self.size += 2
    record.write(self)
    self.size -= 2
    
    length = len(''.join(self.data[index:]))
    self.insertShort(index, length) # Here is the short we adjusted for

  def packet(self):
    """Returns a string containing the packet's bytes

    No further parts should be added to the packet once this
    is done."""
    if not self.finished:
      self.finished = 1
      for question in self.questions:
        self.writeQuestion(question)
      for answer, time in self.answers:
        self.writeRecord(answer, time)
      for authority in self.authorities:
        self.writeRecord(authority, 0)
      for additional in self.additionals:
        self.writeRecord(additional, 0)
    
      self.insertShort(0, len(self.additionals))
      self.insertShort(0, len(self.authorities))
      self.insertShort(0, len(self.answers))
      self.insertShort(0, len(self.questions))
      self.insertShort(0, self.flags)
      if self.multicast:
        self.insertShort(0, 0)
      else:
        self.insertShort(0, self.id)
    return ''.join(self.data)


class DNSCache(object):
  """A cache of DNS entries"""
  
  def __init__(self):
    self.cache = {}

  def add(self, entry):
    """Adds an entry"""
    try:
      list = self.cache[entry.key]
    except:
      list = self.cache[entry.key] = []
    list.append(entry)

  def remove(self, entry):
    """Removes an entry"""
    try:
      list = self.cache[entry.key]
      list.remove(entry)
    except:
      pass

  def get(self, entry):
    """Gets an entry by key.  Will return None if there is no
    matching entry."""
    try:
      list = self.cache[entry.key]
      return list[list.index(entry)]
    except:
      return None

  def getByDetails(self, name, type, clazz):
    """Gets an entry by details.  Will return None if there is
    no matching entry."""
    entry = DNSEntry(name, type, clazz)
    return self.get(entry)

  def entriesWithName(self, name):
    """Returns a list of entries whose key matches the name."""
    try:
      return self.cache[name]
    except:
      return []

  def entries(self):
    """Returns a list of all entries"""
    def add(x, y): return x+y
    try:
      return reduce(add, self.cache.values())
    except:
      return []


class Engine(threading.Thread):
  """An engine wraps read access to sockets, allowing objects that
  need to receive data from sockets to be called back when the
  sockets are ready.

  A reader needs a handle_read() method, which is called when the socket
  it is interested in is ready for reading.

  Writers are not implemented here, because we only send short
  packets.
  """

  def __init__(self, zeroconf):
    threading.Thread.__init__(self)
    self.zeroconf = zeroconf
    self.readers = {} # maps socket to reader
    self.timeout = 5
    self.condition = threading.Condition()
    self.setDaemon(True) # Don't block exit on this thread.
    self.start()

  def run(self):
    while not globals()['_GLOBAL_DONE']:
      rs = self.getReaders()
      if len(rs) == 0:
        # No sockets to manage, but we wait for the timeout
        # or addition of a socket
        #
        self.condition.acquire()
        self.condition.wait(self.timeout)
        self.condition.release()
      else:
        try:
          rr, wr, er = select.select(rs, [], [], self.timeout)
          for socket in rr:
            try:
              self.readers[socket].handle_read()
            except:
              traceback.print_exc()
        except:
          pass

  def getReaders(self):
    result = []
    self.condition.acquire()
    result = self.readers.keys()
    self.condition.release()
    return result
  
  def addReader(self, reader, socket):
    self.condition.acquire()
    self.readers[socket] = reader
    self.condition.notify()
    self.condition.release()

  def delReader(self, socket):
    self.condition.acquire()
    del(self.readers[socket])
    self.condition.notify()
    self.condition.release()

  def notify(self):
    self.condition.acquire()
    self.condition.notify()
    self.condition.release()

class Listener(object):
  """A Listener is used by this module to listen on the multicast
  group to which DNS messages are sent, allowing the implementation
  to cache information as it arrives.

  It requires registration with an Engine object in order to have
  the read() method called when a socket is availble for reading."""
  
  def __init__(self, zeroconf):
    self.zeroconf = zeroconf
    self.zeroconf.engine.addReader(self, self.zeroconf.socket)

  def handle_read(self):
    data, (addr, port) = self.zeroconf.socket.recvfrom(_MAX_MSG_ABSOLUTE)
    self.data = data
    msg = DNSIncoming(data)
    if msg.isQuery():
      # Always multicast responses
      #
      if port == _MDNS_PORT:
        self.zeroconf.handleQuery(msg, _MDNS_ADDR, _MDNS_PORT)
      # If it's not a multicast query, reply via unicast
      # and multicast
      #
      elif port == _DNS_PORT:
        self.zeroconf.handleQuery(msg, addr, port)
        self.zeroconf.handleQuery(msg, _MDNS_ADDR, _MDNS_PORT)
    else:
      self.zeroconf.handleResponse(msg)


class Reaper(threading.Thread):
  """A Reaper is used by this module to remove cache entries that
  have expired."""
  
  def __init__(self, zeroconf):
    threading.Thread.__init__(self)
    self.zeroconf = zeroconf
    self.setDaemon(True) # Don't block exit on this thread.
    self.start()

  def run(self):
    while 1:
      self.zeroconf.wait(10 * 1000)
      if globals()['_GLOBAL_DONE']:
        return
      now = currentTimeMillis()
      for record in self.zeroconf.cache.entries():
        if record.isExpired(now):
          self.zeroconf.updateRecord(now, record)
          self.zeroconf.cache.remove(record)


class ServiceBrowser(threading.Thread):
  """Used to browse for a service of a specific type.

  The listener object will have its addService() and
  removeService() methods called when this browser
  discovers changes in the services availability."""
  
  def __init__(self, zeroconf, type, listener):
    """Creates a browser for a specific type"""
    threading.Thread.__init__(self)
    self.zeroconf = zeroconf
    self.type = type
    self.listener = listener
    self.services = {}
    self.nextTime = currentTimeMillis()
    self.delay = _BROWSER_TIME
    self.list = []
    
    self.done = 0

    self.zeroconf.addListener(self, DNSQuestion(self.type, _TYPE_PTR, _CLASS_IN))
    self.setDaemon(True) # Don't block exit on this thread.
    self.start()

  def updateRecord(self, zeroconf, now, record):
    """Callback invoked by Zeroconf when new information arrives.

    Updates information required by browser in the Zeroconf cache."""
    if record.type == _TYPE_PTR and record.name == self.type:
      expired = record.isExpired(now)
      try:
        oldrecord = self.services[record.alias.lower()]
        if not expired:
          oldrecord.resetTTL(record)
        else:
          del(self.services[record.alias.lower()])
          callback = lambda x: self.listener.removeService(x, self.type, record.alias)
          self.list.append(callback)
          return
      except:
        if not expired:
          self.services[record.alias.lower()] = record
          callback = lambda x: self.listener.addService(x, self.type, record.alias)
          self.list.append(callback)

      expires = record.getExpirationTime(75)
      if expires < self.nextTime:
        self.nextTime = expires

  def cancel(self):
    self.done = 1
    self.zeroconf.notifyAll()

  def run(self):
    while 1:
      event = None
      now = currentTimeMillis()
      if len(self.list) == 0 and self.nextTime > now:
        self.zeroconf.wait(self.nextTime - now)
      if globals()['_GLOBAL_DONE'] or self.done:
        return
      now = currentTimeMillis()

      if self.nextTime <= now:
        out = DNSOutgoing(_FLAGS_QR_QUERY)
        out.addQuestion(DNSQuestion(self.type, _TYPE_PTR, _CLASS_IN))
        for record in self.services.values():
          if not record.isExpired(now):
            out.addAnswerAtTime(record, now)
        self.zeroconf.send(out)
        self.nextTime = now + self.delay
        self.delay = min(20 * 1000, self.delay * 2)

      if len(self.list) > 0:
        event = self.list.pop(0)

      if event is not None:
        event(self.zeroconf)
        

class ServiceInfo(object):
  """Service information"""
  
  def __init__(self, type, name, address=None, port=None, weight=0, priority=0, properties=None, server=None):
    """Create a service description.

    type: fully qualified service type name
    name: fully qualified service name
    address: IP address as unsigned short, network byte order
    port: port that the service runs on
    weight: weight of the service
    priority: priority of the service
    properties: dictionary of properties (or a string holding the bytes for the text field)
    server: fully qualified name for service host (defaults to name)"""

    if not name.endswith(type):
      raise BadTypeInNameException
    self.type = type
    self.name = name
    self.address = address
    self.port = port
    self.weight = weight
    self.priority = priority
    if server:
      self.server = server
    else:
      self.server = name
    self.setProperties(properties)

  def setProperties(self, properties):
    """Sets properties and text of this info from a dictionary"""
    if isinstance(properties, dict):
      self.properties = properties
      list = []
      result = ''
      for key in properties:
        value = properties[key]
        if value is None:
          suffix = ''.encode('utf-8')
        elif isinstance(value, str):
          suffix = value.encode('utf-8')
        elif isinstance(value, int):
          if value:
            suffix = 'true'
          else:
            suffix = 'false'
        else:
          suffix = ''.encode('utf-8')
        list.append('='.join((key, suffix)))
      for item in list:
        result = ''.join((result, struct.pack('!c', chr(len(item))), item))
      self.text = result
    else:
      self.text = properties

  def setText(self, text):
    """Sets properties and text given a text field"""
    self.text = text
    try:
      result = {}
      end = len(text)
      index = 0
      strs = []
      while index < end:
        length = ord(text[index])
        index += 1
        strs.append(text[index:index+length])
        index += length
      
      for s in strs:
        eindex = s.find('=')
        if eindex == -1:
          # No equals sign at all
          key = s
          value = 0
        else:
          key = s[:eindex]
          value = s[eindex+1:]
          if value == 'true':
            value = 1
          elif value == 'false' or not value:
            value = 0

        # Only update non-existent properties
        if key and result.get(key) == None:
          result[key] = value

      self.properties = result
    except:
      traceback.print_exc()
      self.properties = None
      
  def getType(self):
    """Type accessor"""
    return self.type

  def getName(self):
    """Name accessor"""
    if self.type is not None and self.name.endswith("." + self.type):
      return self.name[:len(self.name) - len(self.type) - 1]
    return self.name

  def getAddress(self):
    """Address accessor"""
    return self.address

  def getPort(self):
    """Port accessor"""
    return self.port

  def getPriority(self):
    """Pirority accessor"""
    return self.priority

  def getWeight(self):
    """Weight accessor"""
    return self.weight

  def getProperties(self):
    """Properties accessor"""
    return self.properties

  def getText(self):
    """Text accessor"""
    return self.text

  def getServer(self):
    """Server accessor"""
    return self.server

  def updateRecord(self, zeroconf, now, record):
    """Updates service information from a DNS record"""   
    if record is not None and not record.isExpired(now):
      if record.type == _TYPE_A:
        if record.name == self.server:
          self.address = record.address
      elif record.type == _TYPE_SRV:
        if record.name == self.name:
          self.server = record.server
          self.port = record.port
          self.weight = record.weight
          self.priority = record.priority
          self.address = None
          self.updateRecord(zeroconf, now, zeroconf.cache.getByDetails(self.server, _TYPE_A, _CLASS_IN))
      elif record.type == _TYPE_TXT:
        if record.name == self.name:
          self.setText(record.text)

  def request(self, zeroconf, timeout):
    """Returns true if the service could be discovered on the
    network, and updates this object with details discovered.
    """
    now = currentTimeMillis()
    delay = _LISTENER_TIME
    next = now + delay
    last = now + timeout
    result = 0
    try:
      zeroconf.addListener(self, DNSQuestion(self.name, _TYPE_ANY, _CLASS_IN))
      while self.server is None or self.address is None or self.text is None:
        if last <= now:
          return 0
        if next <= now:
          out = DNSOutgoing(_FLAGS_QR_QUERY)
          out.addQuestion(DNSQuestion(self.name, _TYPE_SRV, _CLASS_IN))
          out.addAnswerAtTime(zeroconf.cache.getByDetails(self.name, _TYPE_SRV, _CLASS_IN), now)
          out.addQuestion(DNSQuestion(self.name, _TYPE_TXT, _CLASS_IN))
          out.addAnswerAtTime(zeroconf.cache.getByDetails(self.name, _TYPE_TXT, _CLASS_IN), now)
          if self.server is not None:
            out.addQuestion(DNSQuestion(self.server, _TYPE_A, _CLASS_IN))
            out.addAnswerAtTime(zeroconf.cache.getByDetails(self.server, _TYPE_A, _CLASS_IN), now)
          zeroconf.send(out)
          next = now + delay
          delay = delay * 2

        zeroconf.wait(min(next, last) - now)
        now = currentTimeMillis()
      result = 1
    finally:
      zeroconf.removeListener(self)
    return result

  def __eq__(self, other):
    """Tests equality of service name"""
    if isinstance(other, ServiceInfo):
      return other.name == self.name
    return 0

  def __ne__(self, other):
    """Non-equality test"""
    return not self.__eq__(other)

  def __repr__(self):
    """String representation"""
    if self.getAddress():
      result = "service[%s,%s:%s," % (self.name, socket.inet_ntoa(self.getAddress()), self.port)
    else:
      result = "service[%s,n/a:%s]," % (self.name, self.port)
    if self.text is None:
      result += "None"
    else:
      if len(self.text) < 20:
        result += self.text
      else:
        result += self.text[:17] + "..."
    result += "]"
    return result
        

class Zeroconf(object):
  """Implementation of Zeroconf Multicast DNS Service Discovery

  Supports registration, unregistration, queries and browsing.
  """
  def __init__(self, bindaddress=None):
    """Creates an instance of the Zeroconf class, establishing
    multicast communications, listening and reaping threads."""
    globals()['_GLOBAL_DONE'] = 0
    self.group = ('', _MDNS_PORT)
    self.socket = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
    try:
      self.socket.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
      self.socket.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEPORT, 1)
    except:
      # SO_REUSEADDR should be equivalent to SO_REUSEPORT for
      # multicast UDP sockets (p 731, "TCP/IP Illustrated,
      # Volume 2"), but some BSD-derived systems require
      # SO_REUSEPORT to be specified explicity.  Also, not all
      # versions of Python have SO_REUSEPORT available.  So
      # if you're on a BSD-based system, and haven't upgraded
      # to Python 2.3 yet, you may find this library doesn't
      # work as expected.
      #
      pass
    self.socket.setsockopt(socket.SOL_IP, socket.IP_MULTICAST_TTL, 255)
    self.socket.setsockopt(socket.SOL_IP, socket.IP_MULTICAST_LOOP, 1)
    try:
      self.socket.bind(self.group)
    except:
      # Some versions of linux raise an exception even though
      # the SO_REUSE* options have been set, so ignore it
      #
      pass
    self.socket.setsockopt(socket.SOL_IP, socket.IP_ADD_MEMBERSHIP, socket.inet_aton(_MDNS_ADDR) + socket.inet_aton('0.0.0.0'))

    self.listeners = []
    self.browsers = []
    self.services = {}

    self.cache = DNSCache()

    self.condition = threading.Condition()
    
    self.engine = Engine(self)
    self.listener = Listener(self)
    self.reaper = Reaper(self)

  def isLoopback(self):
    return self.intf.startswith("127.0.0.1")

  def isLinklocal(self):
    return self.intf.startswith("169.254.")

  def wait(self, timeout):
    """Calling thread waits for a given number of milliseconds or
    until notified."""
    self.condition.acquire()
    self.condition.wait(timeout/1000)
    self.condition.release()

  def notifyAll(self):
    """Notifies all waiting threads"""
    self.condition.acquire()
    self.condition.notifyAll()
    self.condition.release()

  def getServiceInfo(self, type, name, timeout=3000):
    """Returns network's service information for a particular
    name and type, or None if no service matches by the timeout,
    which defaults to 3 seconds."""
    info = ServiceInfo(type, name)
    if info.request(self, timeout):
      return info
    return None

  def addServiceListener(self, type, listener):
    """Adds a listener for a particular service type.  This object
    will then have its updateRecord method called when information
    arrives for that type."""
    self.removeServiceListener(listener)
    self.browsers.append(ServiceBrowser(self, type, listener))

  def removeServiceListener(self, listener):
    """Removes a listener from the set that is currently listening."""
    for browser in self.browsers:
      if browser.listener == listener:
        browser.cancel()
        del(browser)

  def registerService(self, info, ttl=_DNS_TTL):
    """Registers service information to the network with a default TTL
    of 60 seconds.  Zeroconf will then respond to requests for
    information for that service.  The name of the service may be
    changed if needed to make it unique on the network."""
    self.checkService(info)
    self.services[info.name.lower()] = info
    now = currentTimeMillis()
    nextTime = now
    i = 0
    while i < 3:
      if now < nextTime:
        self.wait(nextTime - now)
        now = currentTimeMillis()
        continue
      out = DNSOutgoing(_FLAGS_QR_RESPONSE | _FLAGS_AA)
      out.addAnswerAtTime(DNSPointer(info.type, _TYPE_PTR, _CLASS_IN, ttl, info.name), 0)
      out.addAnswerAtTime(DNSService(info.name, _TYPE_SRV, _CLASS_IN, ttl, info.priority, info.weight, info.port, info.server), 0)
      out.addAnswerAtTime(DNSText(info.name, _TYPE_TXT, _CLASS_IN, ttl, info.text), 0)
      if info.address:
        out.addAnswerAtTime(DNSAddress(info.server, _TYPE_A, _CLASS_IN, ttl, info.address), 0)
      self.send(out)
      i += 1
      nextTime += _REGISTER_TIME

  def unregisterService(self, info):
    """Unregister a service."""
    try:
      del(self.services[info.name.lower()])
    except:
      pass
    now = currentTimeMillis()
    nextTime = now
    i = 0
    while i < 3:
      if now < nextTime:
        self.wait(nextTime - now)
        now = currentTimeMillis()
        continue
      out = DNSOutgoing(_FLAGS_QR_RESPONSE | _FLAGS_AA)
      out.addAnswerAtTime(DNSPointer(info.type, _TYPE_PTR, _CLASS_IN, 0, info.name), 0)
      out.addAnswerAtTime(DNSService(info.name, _TYPE_SRV, _CLASS_IN, 0, info.priority, info.weight, info.port, info.name), 0)
      out.addAnswerAtTime(DNSText(info.name, _TYPE_TXT, _CLASS_IN, 0, info.text), 0)
      if info.address:
        out.addAnswerAtTime(DNSAddress(info.server, _TYPE_A, _CLASS_IN, 0, info.address), 0)
      self.send(out)
      i += 1
      nextTime += _UNREGISTER_TIME

  def unregisterAllServices(self):
    """Unregister all registered services."""
    if len(self.services) > 0:
      now = currentTimeMillis()
      nextTime = now
      i = 0
      while i < 3:
        if now < nextTime:
          self.wait(nextTime - now)
          now = currentTimeMillis()
          continue
        out = DNSOutgoing(_FLAGS_QR_RESPONSE | _FLAGS_AA)
        for info in self.services.values():
          out.addAnswerAtTime(DNSPointer(info.type, _TYPE_PTR, _CLASS_IN, 0, info.name), 0)
          out.addAnswerAtTime(DNSService(info.name, _TYPE_SRV, _CLASS_IN, 0, info.priority, info.weight, info.port, info.server), 0)
          out.addAnswerAtTime(DNSText(info.name, _TYPE_TXT, _CLASS_IN, 0, info.text), 0)
          if info.address:
            out.addAnswerAtTime(DNSAddress(info.server, _TYPE_A, _CLASS_IN, 0, info.address), 0)
        self.send(out)
        i += 1
        nextTime += _UNREGISTER_TIME

  def checkService(self, info):
    """Checks the network for a unique service name, modifying the
    ServiceInfo passed in if it is not unique."""
    now = currentTimeMillis()
    nextTime = now
    i = 0
    while i < 3:
      for record in self.cache.entriesWithName(info.type):
        if record.type == _TYPE_PTR and not record.isExpired(now) and record.alias == info.name:
          if (info.name.find('.') < 0):
            info.name = info.name + ".[" + info.address + ":" + info.port + "]." + info.type
            self.checkService(info)
            return
          raise NonUniqueNameException
      if now < nextTime:
        self.wait(nextTime - now)
        now = currentTimeMillis()
        continue
      out = DNSOutgoing(_FLAGS_QR_QUERY | _FLAGS_AA)
      self.debug = out
      out.addQuestion(DNSQuestion(info.type, _TYPE_PTR, _CLASS_IN))
      out.addAuthorativeAnswer(DNSPointer(info.type, _TYPE_PTR, _CLASS_IN, _DNS_TTL, info.name))
      self.send(out)
      i += 1
      nextTime += _CHECK_TIME

  def addListener(self, listener, question):
    """Adds a listener for a given question.  The listener will have
    its updateRecord method called when information is available to
    answer the question."""
    now = currentTimeMillis()
    self.listeners.append(listener)
    if question is not None:
      for record in self.cache.entriesWithName(question.name):
        if question.answeredBy(record) and not record.isExpired(now):
          listener.updateRecord(self, now, record)
    self.notifyAll()

  def removeListener(self, listener):
    """Removes a listener."""
    try:
      self.listeners.remove(listener)
      self.notifyAll()
    except:
      pass

  def updateRecord(self, now, rec):
    """Used to notify listeners of new information that has updated
    a record."""
    for listener in self.listeners:
      listener.updateRecord(self, now, rec)
    self.notifyAll()

  def handleResponse(self, msg):
    """Deal with incoming response packets.  All answers
    are held in the cache, and listeners are notified."""
    now = currentTimeMillis()
    for record in msg.answers:
      expired = record.isExpired(now)
      if record in self.cache.entries():
        if expired:
          self.cache.remove(record)
        else:
          entry = self.cache.get(record)
          if entry is not None:
            entry.resetTTL(record)
            record = entry
      else:
        self.cache.add(record)
        
      self.updateRecord(now, record)

  def handleQuery(self, msg, addr, port):
    """Deal with incoming query packets.  Provides a response if
    possible."""
    out = None

    # Support unicast client responses
    #
    if port != _MDNS_PORT:
      out = DNSOutgoing(_FLAGS_QR_RESPONSE | _FLAGS_AA, 0)
      for question in msg.questions:
        out.addQuestion(question)
    
    for question in msg.questions:
      if question.type == _TYPE_PTR:
        for service in self.services.values():
          if question.name == service.type:
            if out is None:
              out = DNSOutgoing(_FLAGS_QR_RESPONSE | _FLAGS_AA)
            out.addAnswer(msg, DNSPointer(service.type, _TYPE_PTR, _CLASS_IN, _DNS_TTL, service.name))
      else:
        try:
          if out is None:
            out = DNSOutgoing(_FLAGS_QR_RESPONSE | _FLAGS_AA)
          
          # Answer A record queries for any service addresses we know
          if question.type == _TYPE_A or question.type == _TYPE_ANY:
            for service in self.services.values():
              if service.server == question.name.lower():
                out.addAnswer(msg, DNSAddress(question.name, _TYPE_A, _CLASS_IN | _CLASS_UNIQUE, _DNS_TTL, service.address))
          
          service = self.services.get(question.name.lower(), None)
          if not service: continue
          
          if question.type == _TYPE_SRV or question.type == _TYPE_ANY:
            out.addAnswer(msg, DNSService(question.name, _TYPE_SRV, _CLASS_IN | _CLASS_UNIQUE, _DNS_TTL, service.priority, service.weight, service.port, service.server))
          if question.type == _TYPE_TXT or question.type == _TYPE_ANY:
            out.addAnswer(msg, DNSText(question.name, _TYPE_TXT, _CLASS_IN | _CLASS_UNIQUE, _DNS_TTL, service.text))
          if question.type == _TYPE_SRV:
            out.addAdditionalAnswer(DNSAddress(service.server, _TYPE_A, _CLASS_IN | _CLASS_UNIQUE, _DNS_TTL, service.address))
        except:
          traceback.print_exc()
        
    if out is not None and out.answers:
      out.id = msg.id
      self.send(out, addr, port)

  def send(self, out, addr = _MDNS_ADDR, port = _MDNS_PORT):
    """Sends an outgoing packet."""
    # This is a quick test to see if we can parse the packets we generate
    #temp = DNSIncoming(out.packet())
    try:
      bytes_sent = self.socket.sendto(out.packet(), 0, (addr, port))
    except:
      # Ignore this, it may be a temporary loss of network connection
      pass

  def close(self):
    """Ends the background threads, and prevent this instance from
    servicing further queries."""
    if globals()['_GLOBAL_DONE'] == 0:
      globals()['_GLOBAL_DONE'] = 1
      self.notifyAll()
      self.engine.notify()
      self.unregisterAllServices()
      self.socket.setsockopt(socket.SOL_IP, socket.IP_DROP_MEMBERSHIP, socket.inet_aton(_MDNS_ADDR) + socket.inet_aton('0.0.0.0'))
      self.socket.close()
      
# Test a few module features, including service registration, service
# query (for Zoe), and service unregistration.

if __name__ == '__main__':  
  print "Multicast DNS Service Discovery for Python, version", __version__
  r = Zeroconf()
  print "1. Testing registration of a service..."
  desc = {'version':'0.10','a':'test value', 'b':'another value'}
  info = ServiceInfo("_http._tcp.local.", "My Service Name._http._tcp.local.", socket.inet_aton("127.0.0.1"), 1234, 0, 0, desc)
  print "   Registering service..."
  r.registerService(info)
  print "   Registration done."
  print "2. Testing query of service information..."
  print "   Getting ZOE service:", str(r.getServiceInfo("_http._tcp.local.", "ZOE._http._tcp.local."))
  print "   Query done."
  print "3. Testing query of own service..."
  print "   Getting self:", str(r.getServiceInfo("_http._tcp.local.", "My Service Name._http._tcp.local."))
  print "   Query done."
  print "4. Testing unregister of service information..."
  r.unregisterService(info)
  print "   Unregister done."
  r.close()
